Method for assembling vehicle seat with cushion plate

ABSTRACT

A method of assembling a vehicle seat is provided, comprising: providing a seat back frame; forwardly movably connecting a headrest for supporting a head of a seat occupant to the seat back frame; mounting a rear-end collision detector to the seat back frame at a position behind the seat occupant, operatively connecting the rear-end collision detector to the headrest; disposing a link member at a position lateral to the rear-end collision detector; forming a front extending portion that inwardly extends in a right-to-left direction at a front end of a lateral face of the side frame; and forming a rear extending portion that inwardly extends in the right-to-left direction; wherein a protruding portion is formed from a portion of the lateral face of the side frame that faces at least the part of the bracket, the link support shaft being disposed at a same height as the protruding portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/851,840, filed Mar. 27, 2013, which is a divisionalapplication of U.S. Pat. No. 8,444,219, filed Feb. 2, 2012, which is adivisional application of U.S. Pat. No. 8,132,857, filed May 12, 2011,which is a divisional application of U.S. Pat. No. 7,963,599, filed Feb.17, 2010, which is a divisional application of U.S. Pat. No. 7,967,380,filed Nov. 21, 2007, which is a PCT national stage entry ofinternational patent application no. PCT/JP2005/19937, filed Oct. 28,2005, which claims the foreign priority benefit of Japanese patentapplication no. JP2004-313623, filed Oct. 28, 2004. The contents ofthese applications are herein incorporated by reference.

TECHNICAL FIELD

The present invention relates to a method for assembling vehicle seat,and particularly a vehicle seat having a cushion plate with a pressureadjusting mechanism.

BACKGROUND

A conventional seat back cushion for a vehicle seat is resilientlysupported by means of a number of seat springs which are located betweenside frames of a seat back frame. The seat springs generally comprisezigzag springs or formed wire springs.

The degree of bending of the seat springs locally vary depending on themagnitude of load imparted. The springs located in the upper and lowerportions of the seat back frame are more bent than those located in thecentral portion of the seat back frame. Even in one spring, the centralpart of the spring is more bent than the right and left side parts ofthe spring. Thus, the degree of bending of the springs are locallyvaried. This brings about deterioration of the stability and comfort ofthe seat when a person sits on the seat.

Japanese Patent Application Laid-Open No. 11-206506 discloses astructural arrangement where an auxiliary plate, which is forwardly andrearwardly movable, is provided in connection with the cushion plate.

The auxiliary plate disclosed in Japanese Patent Application Laid-OpenNo. 11-206506 is integrally formed at the central part of the cushionplate, and the cushion plate is disposed only around the auxiliaryplate. Therefore, the cushion plate disposed around the auxiliary platefails to exhibit its function as the mechanism for resilientlysupporting the seat back cushion. This means that a load of the seatedperson is focused on the auxiliary plate and is not effectivelydispersed in the cushion plate.

Also in the conventional technique, it is difficult to provide both of apressure adjusting mechanism of the cushion plate and an active headrestmechanism for moving the headrest to the front when the vehicle rear-endcollision occurs in the seat back. In other words, the pressureadjusting mechanism lowers a sensitivity of a collision detector of theactive headrest mechanism, and hence, it is difficult to coexistentlyprovide both of the mechanisms.

SUMMARY

Disclosed herein is a method to assemble a vehicle seat having a cushionplate with a pressure adjusting mechanism which is able to support theseated person while effectively dispersing the load of the seatedperson.

In an embodiment, a method is disclosed for assembling a vehicle seathaving a cushion plate with a pressure adjusting mechanism and an activeheadrest mechanism for moving the headrest to the front when the vehiclerear-end collision occurs.

In more detail, various embodiments of the invention provide a method ofassembling a vehicle seat, comprising: providing a seat back frame;forwardly movably connecting a headrest for supporting a head of a seatoccupant to the seat back frame; mounting a rear-end collision detectorto the seat back frame at a position behind the seat occupant, whereinthe rear-end collision detector detects rearward movement of the seatoccupant and is movable rearward; operatively connecting the rear-endcollision detector to the headrest such that the rearward movement ofthe rear-end collision detector forwardly moves the headrest; disposinga link member at a position lateral to the rear-end collision detector;mounting a bracket to a side frame that constitutes a side portion ofthe seat back frame; mounting a link support shaft to the bracket, withthe link member being mounted to the link support shaft; forming a frontextending portion that inwardly extends in a right-to-left direction andis formed at a front end of a lateral face of the side frame; andforming a rear extending portion that inwardly extends in theright-to-left direction and is formed at a rear end of the lateral faceof the side frame; wherein: at least a part of the bracket is disposedon the lateral face of the side frame and between the front extendingportion and the rear extending portion; a protruding portion inwardlyprotruding is formed from a portion of the lateral face of the sideframe that faces at least the part of the bracket, the link supportshaft being disposed at a same height as the protruding portion; and atleast the part of the bracket is directly attached to the integrallyformed protruding portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings illustrate an embodiment of the invention that isdescribed in more detail below.

FIG. 1 is a perspective view showing a vehicle seat;

FIG. 2 is an exploded perspective view showing a seat back frame of thevehicle seat and basic components of an active headrest mechanism;

FIG. 3 is a perspective view showing an assembly of the components shownin FIG. 2;

FIG. 4 is a perspective view showing a state that a cushion plate and anauxiliary plate are mounted to the assembly of FIG. 3;

FIG. 5 is a side view showing a side frame of the seat back frame andthe basic components of the active headrest mechanism;

FIG. 6 is a perspective view showing the back sides of the cushion plateand the auxiliary plate;

FIG. 7 is a side view showing a relationship between a part of skeletonof a seated person and the cushion plate; and

FIG. 8 is a longitudinal sectional view showing the cushion plate andthe auxiliary plate.

DETAILED DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention will be described with referenceto the accompanying drawings. Referring to FIGS. 1-4, a vehicle seat 1of the present invention has a seat back 2, a seat bottom 3 and aheadrest 4 provided at the top of the seat back 2. Referring to FIGS. 2and 3, a seat back frame 5 of the seat back 2 includes a pair of sideframes 6, an upper frame 7 and a lower frame 8 having a connecting plate8 a and a projecting curve portion 8 b, the lower frame having asubstantial rectangular shape.

A headrest support (or “lateral member” or “right-to-left extendingmember”) 10 is arranged near the upper frame 7. The support 10horizontally extends and is movable with respect to the seat back frame5. Lower parts of pillars 9 of the headrest 4 are inserted into verticalengaging parts (first/second pillar insertion portions) 11 which arefixed to the headrest support 10. The pillars 9 are verticallyadjustable with the aid of the vertical engaging parts 11.

Upper brackets 12 are fixed to the side frames 6, respectively. Theframes 6 comprise a front projecting wall (front extending portion) 6 b,a rear projecting wall (rear extending portion) 6 c, an opening 6 d, aninwardly protruding/side projecting portion 6 e, a lateral face 6 f, aconcave portion 6 g, which may be a cutout portion formed at a portionof an inner end portion 6 h of the front projecting wall (frontextending portion) 6 b of the side frame 6 that faces at least a part ofthe bracket 12, where the concave portion 6 g is disposed at a positionfacing a link support shaft 16. The frames 6 also comprise a supportmember attachment portion 6 i, a first step portion 6 j, a second stepportion 6 k, and a lower side frame portion 6 m.

An upper link (link member) or bell crank 15 is rotatably mounted toeach upper bracket 12 by a shaft 16 that protrudes through a first hole16 a of the upper link 15 at a link support portion 15 a. Each upperlink 15 includes an upper long arm 22 extending upward and a lower shortarm 23 extending downwardly and to the front side. The upper link 15 isurged by resiliency of an upper spring 13 clockwise, as shown in FIG. 5.The upper spring 13 includes a first end coupled to the upper link 15and a second end coupled to the side frame 6. The right and left ends ofthe headrest support 10 are coupled to the upper arms 22, respectively.Each lower arm 23 is axially fixed to the upper part of a longitudinallyextending coupling (or load transmission) rod 20 by way of a pin 21 thatextends through a second hole 21 a of the upper link 15.

The upper link 15 is normally held at a position indicated by a solidline in FIG. 5 by the resiliency of the upper spring 13 or the like,whereby the headrest 4 is also held at a normal position. However, whenthe upper link 15 is rotated counterclockwise toward a positionindicated by a dotted line, the headrest support 10 forwardly moves andthe headrest 4 is pushed to the front.

A horizontally extending vehicle rear-end collision detector (connectingplate member) 25 is arranged between the side frames 6, 6. The collisiondetector 25 comprises a contact portion 25 a and a reinforcing portion25 b (bead). When a rear-end collision occurs and the vehicle seat 1relatively moves forward against the vehicle seat occupant T (FIG. 7),the collision detector 25 (FIGS. 3, 4) moves rearward by being pushed bythe seat occupant T. Both ends of the collision detector 25 are coupledto lower links 26, 26 by way of pins 27, 27 (also “swinging shaft” or“connecting shaft”) which are axially fixed to the side frames 6, 6 bylink support shafts 28, 28, via connecting members (extending portion ofthe connecting plate member) 25′, 25′ respectively. A lower bracket 35is provided having a link shaft supporting face 35 a, a first attachmentportion 35 b, and a second attachment portion 35 d. The lower bracket 35may attach via a bracket attachment portion 35 c. The connecting members25′ each comprise a bend portion 25′a and a strengthening portion 25′b.The lower part of the coupling rod 20 is coupled to the lower link (linkmember) 26 by way of a pin 29. As shown in FIG. 5, one end of a lowerspring (biasing member) 14 is coupled to the lower link 26 at a firstbiasing member engagement portion 26′, while the other end thereof iscoupled to the side frame 6 at a second biasing member engagementportion 6″, whereby the lower links 26 are urged counterclockwise. As aresult, the collision detector 25 is held at a normal position, locatedin the front side.

When a rear-end collision occurs, the vehicle rear-end collisiondetector 25 is pushed by the seat occupant T to move rearward and toturn the lower links 26 counterclockwise in FIG. 5 and to lower thecoupling rod 20. At this time, a distance between the pin 29 and theshaft 28 is shorter than a distance between the pin 27 and the shaft 28,so that a backward movement of the collision detector 25 is efficientlytransmitted to the coupling rod 20. A downward movement of the rod 20rotates the upper link 15 counterclockwise so that the headrest support10 moves forward. The upper arm 22 of the upper link 15 is longer thanthe lower arm 23 so that the downward movement of the coupling rod 20efficiently causes the headrest support 10 to move forward. The forwardmovement of the headrest support 10 pushes the headrest 4 to the front,thereby protecting a head (neck) of the seat occupant T at the time ofthe rear-end collision.

The side frames 6 are formed with a metal plate having a predeterminedwidth as viewed in the front-and-back direction. A transmissionmechanism for transmitting a backward movement of the vehicle rear-endcollision detector 25 to the headrest support 10 is located at aposition near the side frames 6. Accordingly, a cushion 17 of the seatback 2 does not interfere with a motion of the transmission mechanism. Amechanism ranging from the collision detector 25 to the headrest support10 forms an active headrest mechanism.

A flexible plate member 30 comprises a flexible cushion plate (resinplate member) 31 and a flexible auxiliary plate (protruding curvatureportion) 41. The flexible cushion plate 31 is arranged inside the seatback frame 5. The cushion plate 31 is preferably made of synthetic resinsuch as polypropylene, and is substantially a single rectangular plate.The cushion plate 31 is attached to seat springs 32 such as zigzagsprings or formed wire springs at mounting portions (wire engagementportions) (first wire coupling portion) 31 a, (second wire couplingportion) 31 a′ that may include a rearward projecting portion 31 b. Thecushion plate 31 has a first plate portion 31 d as well as a firstcontact portion 31 e and a second contact portion 31 f. The seat springs32 include at least an upper seat spring (wire member, first wiremember) 32A and a lower seat spring (second wire member) 32B, the lowerseat spring 32B being attached to the cushion plate 31 at a mountingportion 31 a′ within a protruding portion 31 c, and to the side frame 6at a wire spring engagement portion 6 a′. The seat springs 32horizontally extend and are respectively coupled to the side frames 6 ofthe seat back frame 5 at wire spring engagement portions 6 a, 6 a′. Theseat back cushion 17 is provided in front of the cushion plate 31. Thecushion plate 31 comprises an offset portion 36.

When the flexible cushion plate 31 receives a load from the seatoccupant T, the cushion plate 31 moves rearward against the elasticityof the seat springs 32 and flexibly supports the seat occupant T. Thecushion plate 31 supports the seat back cushion 17 in “plane”.Therefore, the cushion plate makes the seat occupant T feel more stableand comfortable than the conventional one in which the seat back cushion17 is supported by only the seat springs 32.

An upper edge 34 of the flexible cushion plate 31, as shown in FIG. 7,is located somewhat higher than the ninth thoracic vertebra X of theseat occupant T of the average height. The center gravity of the upperbody of the seat occupant T is positioned near the ninth thoracicvertebra X. The cushion plate 31 is able to effectively support a partaround the center of gravity of the seat occupant T.

The upper seat spring 32A is selected to be at substantially the sameheight level as the ninth thoracic vertebra X or somewhat lower than it.In FIG. 7, the upper seat spring 32A is located somewhat lower than theninth thoracic vertebra X. The reason for this is that a load of theupper part of the body to the seat back cushion 17 usually acts on therearward side.

The flexible cushion plate 31 includes a lower part 33 for supporting aportion near the sacrum S of the pelvis. The lower part 33 enhances aholding property at a portion near the hip of the seat occupant T.

The vehicle rear-end collision detector 25 is located in the rear of theflexible cushion plate 31 in a state that a predetermined space ispresent therebetween. Since the cushion plate 31 takes a plate-likeshape for broadly covering the back of the seat occupant T, the flexiblecushion plate 31 receives a load of the seat occupant T on a wide areawhen a rear-end collision occurs, and moves rearwardly. The amount of arearward movement of the flexible cushion plate 31 is the largestbetween a mid portion as vertically viewed and a portion somewhat lowerthan the mid position. Therefore, the collision detector 25 ispreferably located at a mid position as vertically viewed or a positionsomewhat lower than the mid position in order to reliably receive therearward movement of the cushion plate 31. Since a width of the seatback 2 as viewed in the front-and-back direction becomes narrowerupward, it is not preferable that the collision detector 25 is locatedat an upper position on the rear side of the flexible cushion plate 31.

A flexible auxiliary plate 41 is provided between the flexible cushionplate 31 and the seat back cushion 17. Collectively, the flexiblecushion plate 31 and auxiliary plate 41 may be construed as a loadreceiving member. The auxiliary plate 41 is preferably made of syntheticresin such as polypropylene, and is substantially a single rectangularplate, which is smaller than the flexible cushion plate 31. When theauxiliary plate 41 is operated by the seat occupant T, it is bent to thefront and pushes the seat back cushion 17 forwardly, thereby adjusting acushion pressure against the seat occupant T.

The auxiliary plate 41, which has a top portion (or a maximum forwardcurve portion) 41 a, is provided with rearward projecting upper sliders42 and lower sliders 43. The upper sliders 42 protrude in a rearwardprojecting portion 42 a to the rear side of the flexible cushion plate31 through vertical upper slits (first through-hole) 45, (secondthrough-hole) 45′ formed in the cushion plate 31. The lower sliders 43protrude to the rear side of the cushion plate 31 through vertical lowerslits (first through-hole) 46, (second through hole) 46′ formed in thecushion plate 31. An upper horizontal mounting shaft 48 is bridgedbetween the upper sliders 42 and 42, and a lower horizontal mountingshaft 49 is bridged between the lower sliders 43 and 43.

The auxiliary plate 41 is mounted to the cushion plate 31 by using themounting shafts 48 and 49. The sliders 42 and 43 are vertically slidablein the slits 45 and 46, respectively. When the upper sliders 42 aremoved downwardly and the lower sliders 43 are moved upwardly, theauxiliary plate 41 is bent to the front.

An upper U-shaped bracket 51 is rotatably mounted on the upperhorizontal mounting shaft 48. The bracket 51 includes a pair of arms 52mounted to the mounting shaft 48 and a coupling part 53 provided betweenthe arms 52. A cable head 56A of an inner cable 56 of a wire cable 55 isplaced on and secured to the coupling part 53. A lower bracket 66 isrotatably mounted to the lower horizontal mounting shaft 49. The lowerbracket 66 includes a pair of arms 67 mounted to the mounting shaft 49and a coupling part 68 provided between the arms 67. A tube head 57A ofan outer tube 57 of the wire cable 55 is placed on and secured to thelower bracket 66. The other end of the wire cable 55 is coupled to anoperation member 58 provided on the vehicle seat 1.

When the operation member 58 is operated, a distance between the cablehead 56A and the tube head 57A, i.e., a distance between the uppersliders 42 and the lower sliders 43 is adjusted. When the distancebecomes long, the auxiliary plate 41 is parallel to the flexible cushionplate 31, and when it becomes short, the auxiliary plate 41 bends toproject to the front. Thus, by operating the operation member 58, adegree of bending (forward projecting quantity) of the auxiliary plate41 can be adjusted.

The auxiliary plate 41 includes a thin part 60 for defining a curvedshape of the auxiliary plate 41. When the distance between the uppersliders 42 and the lower sliders 43 becomes short, the auxiliary plate41 is curved with respect to the thin part 60. Accordingly, the curvedshape of the auxiliary plate 41 is kept in a predetermined shape, andthe cushion pressure adjustment by the auxiliary plate 41 is madeeffective by setting the thin part 60 at the lumber part of the seatoccupant T.

A spring 61, having an upper end attaching portion 61 a for urging theupper horizontal mounting shaft 48 upwardly is provided between theupper horizontal mounting shaft 48 and the flexible cushion plate 31 (orthe upper seat spring 32A).

The flexible cushion plate 31 bends under a load from the seat occupantT and moves rearward against the elasticity of the seat springs 32, andflexibly supports the seat occupant T. The flexible cushion plate 31supports the seat back cushion 17 in “plane”. Therefore, the cushionplate makes the seat occupant T feel more stable and comfortable thanthe conventional one in which the seat back cushion 17 is supported byonly the seat springs 32.

When a physique of the seat occupant T presents an insufficient pressurefrom the seat back cushion 17, the seated person pulls the inner cable56 by operating the operation member 58 to reduce the distance betweenthe upper sliders 42 and the lower sliders 43. Then, the auxiliary plate41 protrudes forward with respect to the thin part 60, pushes the seatback cushion 17 forward to increase the cushion pressure, whereby thecushion pressure is adjusted as the seat occupant T desires.

When the auxiliary plate 41 is curved by the operation member 58, thecushion pressure is changed. Since the auxiliary plate 41 and theflexible cushion plate 31 are in overlapping relation, the load by theseat occupant T that the auxiliary plate 41 receives is directlydispersed into the flexible cushion plate 31 as a single large plate.Accordingly, the good stability and comfort of the seat back cushion 17are not lost.

When a rear-end collision occurs, the flexible cushion plate 31 greatlymoves rearward by the load from the seat occupant T to come into contactwith the vehicle rear-end collision detector 25 and to move it backward.In turn, the lower links 26, in FIG. 5, rotate counterclockwise to lowerthe coupling rod 20. The downward movement of the coupling rod 20 turnsthe upper links 15 counterclockwise to move the headrest support 10 tothe front. As a result, the headrest 4 pushed to the front to protectthe head (neck) of the seat occupant T against the impact by therear-end collision.

In this case, the distance between the pin 29 and the shafts 28 isshorter than that between the pins 27 and the shafts 28. Accordingly,the lower links 26 efficiently transmits the rearward movement of thecollision detector 25 to the coupling rod 20. Since the upper arms 22 ofthe upper links 15 are longer than the lower arms 23, the downwardmovement of the coupling rod 20 is efficiently transmitted to theheadrest support 10. Therefore, the forward movement of the headrest 4is satisfactorily secured.

Since the cushion plate 31 is shaped like a plate broadly covering theback of the seat occupant T, it reliably receives the rearward movementof the seat occupant T at the time of the rear-end collision in a broadarea to reliably transmit the rearward movement of the seat occupant Tto the collision detector 25.

When the auxiliary plate 41 is bent by the operation member 58, thecushion pressure is changed. Since the flexible cushion plate 31 isshaped like a plate broadly covering the back of the seat occupant T,and receives the load from the seat occupant T in a dispersing manner,the change of the cushion pressure by the auxiliary plate 41 does notsubstantially move the positions of the flexible cushion plate 31 andthe collision detector 25. Accordingly, the relative position of thecushion plate 31 to the collision detector 25 is retained and the changeof the cushion pressure by the auxiliary plate 41 does not substantiallyinterfere with the function of the active headrest mechanism.

TABLE OF REFERENCE CHARACTERS

-   1 vehicle seat-   2 seat back-   3 seat bottom-   4 headrest-   5 seat back frame-   6 side frame-   6 a, 6 a′ wire spring engagement portions-   6 b side frame front projecting wall-   6 c side frame rear projecting wall-   6 d opening-   6 e inwardly protruding portion, side projecting portion-   6 f lateral face-   6 g concave (cutout) portion-   6 h inner end portion-   6 i support member attachment portion-   6 j first step portion-   6 k second step portion-   6 m lower side frame portion-   6″ second biasing member engagement portion-   7 upper frame-   8 lower frame-   8 a connecting plate-   8 b projecting curve portion-   9 pillars-   10 headrest support (also “lateral member” or “right-to-left    extending member”)-   11 vertical engaging parts, first and second pillar insertion    portion-   12 upper bracket-   13 upper spring-   14 lower spring (also “biasing member”)-   15 upper link (also “link member”)-   15 a link support portion-   16 link support shaft-   16 a first hole of upper link-   17 cushion-   20 longitudinally extending coupling rod (or “load transmission    rod”)-   21 pin-   21 a second hole of upper link-   22 upper link upper (second) long arm-   23 upper link lower (first) short arm-   25 rear-end collision detector, connecting plate member-   25 a contact portion-   25 b reinforcing portion (bead)-   25′ connecting member, extending portion of connecting plate member-   25′a bend portion-   25′b strengthening portion-   26 lower link (also “link member”)-   26′ first biasing member engagement portion-   27 pin (also “swinging shaft” or “connecting shaft”)-   28 link support shaft-   29 pin-   30 flexible plate member-   31 flexible cushion plate, resin plate member-   31 a mounting portion (also “wire engagement portion”, “first wire    coupling portion”)-   31 a′ mounting portion (also “wire engagement portion”, “second wire    coupling portion”)-   31 b projecting portion-   31 c protruding portion-   31 d first plate portion-   31 e first contact portion-   31 f second contact portion-   32 seat springs-   32A upper seat spring, wire member, first wire member-   32B lower seat spring, second wire member-   33 lower part of flexible cushion plate-   34 upper edge of flexible cushion plate-   35 lower bracket-   35 a link shaft supporting face-   35 b first attachment portion-   35 c bracket attachment portion-   35 d second attachment portion-   36 offset portion-   41 flexible auxiliary plate, protruding curvature portion-   41 a top portion (maximum forward portion of a curve) of auxiliary    plate-   42 rearward projecting upper slider-   42 a rearward projection portion (“retainer”)-   43 lower slider-   45 vertical upper slit, first through hole-   45′ vertical upper slit, second through hole-   46 vertical lower slit, first through hole-   46′ vertical lower slit, second through hole-   48 upper horizontal mounting shaft (also “linear member”)-   49 lower horizontal mounting shaft-   51 upper U-shaped bracket-   52 arms-   53 coupling part-   55 wire cable-   56 inner cable-   56A cable head-   57 outer tube-   57A tube head-   58 operation member-   60 auxiliary plate thin part-   61 spring-   61 a spring upper end attaching portion-   66 lower bracket-   67 lower bracket arm-   68 coupling part-   T occupant

What is claimed is:
 1. A method of assembling a vehicle seat,comprising: providing a seat back frame; forwardly movably connecting aheadrest for supporting a head of a seat occupant to the seat backframe; mounting a rear-end collision detector to the seat back frame ata position behind the seat occupant, wherein the rear-end collisiondetector detects rearward movement of the seat occupant and is movablerearward; operatively connecting the rear-end collision detector to theheadrest such that the rearward movement of the rear-end collisiondetector forwardly moves the headrest; disposing a link member at aposition lateral to the rear-end collision detector; mounting a bracketto a side frame that constitutes a side portion of the seat back frame;mounting a link support shaft to the bracket, with the link member beingmounted to the link support shaft; forming a front extending portionthat inwardly extends in a right-to-left direction and is formed at afront end of a lateral face of the side frame; and forming a rearextending portion that inwardly extends in the right-to-left directionand is formed at a rear end of the lateral face of the side frame;wherein: at least a part of the bracket is disposed on the lateral faceof the side frame and between the front extending portion and the rearextending portion; a protruding portion inwardly protruding isintegrally formed from a portion of the lateral face of the side framethat faces at least the part of the bracket, the link support shaftbeing disposed at a same height as the protruding portion; and at leastthe part of the bracket is directly attached to the integrally formedprotruding portion.
 2. The method according to claim 1, wherein: thelink member is swingably connected to an end of the rear-end collisiondetector through a connecting shaft; and the connecting shaft isdisposed at a position overlapping, in a right-to-left direction, withthe protruding portion.
 3. The method according to claim 2, wherein theconnecting shaft is smaller in diameter than the link support shaft. 4.The method according to claim 1, further comprising: providing thebracket with a link shaft supporting face that extends from a side frameside towards an inner side of the seat; wherein: the link shaftsupporting face is disposed at a position overlapping, in aright-to-left direction, with the protruding portion.
 5. The methodaccording to claim 1, further comprising: providing a headrest supportfor supporting the headrest that extends in a horizontal direction;wherein: the part of the bracket that is attached to the protrudingportion is disposed below the headrest support and above a lower endportion of each side of the rear-end collision detector.
 6. The methodaccording to claim 1, further comprising: providing a flexible platemember in front of the rear-end collision detector; and providing a seatback cushion in front of the flexible plate member; wherein: theflexible plate member pressure-adjusts the seat back cushion byprotruding forward and pushing the seat back cushion to a frontdirection by an operation of the seat occupant; the flexible platemember is provided with a first plate portion disposed closer to a topof the seat than the rear-end collision detector; and a region of thefirst plate portion positioned generally at the same height as thebracket is smaller in width than a region of the maximum width of theflexible plate member.
 7. The method according to claim 6, furthercomprising: positioning a maximum forward portion of a curve of theflexible plate member formed when the flexible plate member protrudesforward closer to a bottom of the seat than the rear-end collisiondetector.
 8. The method according to claim 1, further comprising:providing the protruding portion with a bracket attachment portion forattaching a part of the bracket; and forming an opening on theprotruding portion at a different height than the bracket attachmentportion.
 9. The method according to claim 1, further comprising:providing the protruding portion with a bracket attachment portion forattaching a part of the bracket; and forming an opening on theprotruding portion above the bracket attachment portion.
 10. The methodaccording to claim 1, wherein the protruding portion has a planarportion that abuts at least two surfaces of the side frame.
 11. A methodof assembling a vehicle seat, comprising: providing a seat back frame;forwardly movably connecting a headrest for supporting a head of a seatoccupant to the seat back frame; mounting a rear-end collision detectorto the seat back frame at a position behind the seat occupant, whereinthe rear-end collision detector detects rearward movement of the seatoccupant and moves rearward; and operatively connecting the rear-endcollision detector to the headrest such that the rearward movement ofthe rear-end collision detector forwardly moves the headrest; disposinga link member at a position lateral to the rear-end collision detector;mounting a bracket to a side frame that constitutes a side portion ofthe seat back frame; mounting a link support shaft to the bracket, withthe link member being mounted to the link support shaft; forming a frontextending portion that inwardly extends in a right-to-left direction andis formed at a front end of a lateral face of the side frame; andforming a rear extending portion that inwardly extends in theright-to-left direction and is formed at a rear end of the lateral faceof the side frame; wherein: at least a part of the bracket is disposedon the lateral face of the side frame and between the front extendingportion and the rear extending portion; a protruding portion inwardlyprotruding is formed at a portion of the lateral face of the side framethat faces at least the part of the bracket, the link support shaftbeing disposed at a same height as the protruding portion; at least thepart of the bracket is attached to the protruding portion; the linkmember is disposed overlapping, in a right-to-left direction, with theprotruding portion and extends downward from the link support shaft; alower end portion of the link member is swingably connected to an end ofthe rear-end collision detector through a connecting shaft; the bracketcomprises a link shaft supporting face that extends from a side frameside towards an inner side of the seat, and a first attachment portionand a second attachment portion for being attached to the side frame;and the second attachment portion is disposed closer to a bottom of theseat than the first attachment portion and extends downward from thelink shaft supporting face along the protruding portion to be attachedto the protruding portion.
 12. The method according to claim 11, whereinthe connecting shaft is disposed at a position overlapping, in aright-to-left direction, with the protruding portion.
 13. The methodaccording to claim 12, wherein the connecting shaft is smaller indiameter than the link support shaft.
 14. The method according to claim11, wherein the link shaft supporting face is disposed at a positionoverlapping, in a right-to-left direction, with the protruding portion.15. The method according to claim 11, further comprising: providing aheadrest support for supporting the headrest that extends in ahorizontal direction; wherein: the second attachment portion of thebracket is disposed below the headrest support and above a lower endportion of each side of the rear-end collision detector.
 16. The methodaccording to claim 11, further comprising: providing a flexible platemember in front of the rear-end collision detector; and providing a seatback cushion in front of the flexible plate member; wherein: theflexible plate member pressure-adjusts the seat back cushion byprotruding forward and pushing the seat back cushion to a frontdirection by an operation of the seat occupant; the flexible platemember is provided with a first plate portion disposed closer to a topof the seat than the rear-end collision detector; and a region of thefirst plate portion positioned generally at the same height as thebracket is smaller in width than a region of the maximum width of theflexible plate member.
 17. The method according to claim 16, furthercomprising: positioning a maximum forward portion of a curve of theflexible plate member formed when the flexible plate member protrudesforward closer to a bottom of the seat than the rear-end collisiondetector.
 18. The method according to claim 11, further comprising:forming an opening on the protruding portion at a different height thanthe second attachment portion of the bracket.
 19. The method accordingto claim 11, wherein the connecting shaft and the link shaft supportingface are disposed at a position overlapping, in a right-to-leftdirection, with the protruding portion.
 20. The method according toclaim 11, further comprising: providing a headrest support forsupporting the headrest that extends in a horizontal direction; wherein:the second attachment portion of the bracket is disposed below theheadrest support and above a lower end portion of each side of therear-end collision detector; and the connecting shaft and the link shaftsupporting face are disposed at a position overlapping, in aright-to-left direction, with the protruding portion.
 21. The methodaccording to claim 11, further comprising: forming an opening on theprotruding portion above the second attachment portion of the bracket.22. The method according to claim 11, wherein the protruding portion hasa planar portion that abuts at least two surfaces of the side frame. 23.The method according to claim 22, wherein the at least two surfaces ofthe side frame are provided on an upper side and a lower side of theplanar portion respectively.
 24. The method according to claim 22,further comprising: providing a first surface of the at least twosurfaces of the side frame either on an upper side or a lower side ofthe planar portion; and providing a second surface of the at least twosurfaces of the side frame either on a front side or a rear side of theplanar portion respectively.
 25. The method according to claim 22,wherein: the at least two surfaces of the side frame are provided on anupper side and a lower side of the planar portion; the method furthercomprising: providing a further surface of the side frame either on afront side or a rear side of the planar portion respectively.
 26. Amethod of assembling a vehicle seat, comprising: providing a seat backframe; forwardly movably connecting a headrest for supporting a head ofa seat occupant to the seat back frame; mounting a rear-end collisiondetector to the seat back frame at a position behind the seat occupant,wherein the rear-end collision detector detects rearward movement of theseat occupant and moves rearward; and operatively connecting therear-end collision detector to the headrest such that the rearwardmovement of the rear-end collision detector forwardly moves theheadrest; disposing a link member at a position lateral to the rear-endcollision detector; mounting a bracket to a side frame that constitutesa side portion of the seat back frame; mounting a link support shaft tothe bracket, wherein the link member is mounted to the link supportshaft; forming a front extending portion that inwardly extends in aright-to-left direction and is formed at a front end of a lateral faceof the side frame; and forming a rear extending portion that inwardlyextends in the right-to-left direction and is formed at a rear end ofthe lateral face of the side frame; wherein: at least a part of thebracket is disposed on the lateral face of the side frame and betweenthe front extending portion and the rear extending portion; a protrudingportion inwardly protruding is formed at a portion of the lateral faceof the side frame that faces at least the part of the bracket, the linksupport shaft being disposed at a same height as the protruding portion;at least the part of the bracket is attached to the protruding portion;and the protruding portion has a planar portion that abuts at least twosurfaces of the side frame.
 27. The method according to claim 26,wherein the at least two surfaces of the side frame are provided on anupper side and a lower side of the planar portion respectively.
 28. Themethod according to claim 26, further comprising: providing a firstsurface of the at least two surfaces of the side frame either on anupper side or a lower side of the planar portion; and providing a secondsurface of the at least two surfaces of the side frame either on a frontside or a rear side of the planar portion respectively.
 29. The methodaccording to claim 26, wherein: the at least two surfaces of the sideframe are provided on an upper side and a lower side of the planarportion; the method further comprising: providing a further surface ofthe side frame either on a front side or a rear side of the planarportion.
 30. The method according to claim 26, wherein: the link memberis swingably connected to an end of the rear-end collision detectorthrough a connecting shaft; and the connecting shaft is disposed at aposition overlapping, in a right-to-left direction, with the protrudingportion.
 31. The method according to claim 30, wherein the connectingshaft is smaller in diameter than the link support shaft.
 32. The methodaccording to claim 26, further comprising: providing a flexible platemember in front of the rear-end collision detector; and providing a seatback cushion in front of the flexible plate member; wherein: theflexible plate member pressure-adjusts the seat back cushion byprotruding forward and pushing the seat back cushion to a frontdirection by an operation of the seat occupant; the flexible platemember is provided with a first plate portion disposed closer to a topof the seat than the rear-end collision detector; and a region of thefirst plate portion positioned generally at the same height as thebracket is smaller in width than a region of the maximum width of theflexible plate member.
 33. The method according to claim 32, furthercomprising: positioning a maximum forward portion of a curve of theflexible plate member formed when the flexible plate member protrudesforward closer to a bottom of the seat than the rear-end collisiondetector.